在mysql中使用select join时将数据选择为单行

Question

How can I get data from a mysql query in a single row when selecting data from two tables using a join?

"id"    "itemId"    "itemTempId"    "itemName"                  "userId" "postId"
"1"     "US1"       "T001"          "Samsung Galaxy Note 5"     "1"      "1"

"id"    "itemId"    "itemTempId"    "itemImageName"     "userId" "postId"
"1"     "US1"       "T001"          "front.jpg"         "1"      "1"
"2"     "US1"       "T001"          "side-left.jpg"     "1"      "1"
"3"     "US1"       "T001"          "side-right.jpg"    "1"      "1"
"4"     "US1"       "T001"          "back.jpg"          "1"      "1"

Right now, when I do like below to select 1 row from the first table and related rows from the second table, I get all data in every row which also repeats when I print it using php.

select a.itemName, b.itemImageName from amga a left join amgb b on a.userId = b.userId where a.userId = 1;

Current Output

"itemName"                  "itemImageName"
"Samsung Galaxy Note 5"     "front.jpg"
"Samsung Galaxy Note 5"     "side-left.jpg"
"Samsung Galaxy Note 5"     "side-right.jpg"
"Samsung Galaxy Note 5"     "back.jpg"

Desirable Output or some other variation that wont repeat the itemName and that can easily be output using php.

"itemName"                  "itemImageName"
"Samsung Galaxy Note 5"     "front.jpg","side-left.jpg","side-right.jpg","back.jpg"

In the final results the title is output only once, whereas the image names need to be looped through. Like this:

"Samsung Galaxy Note 5"
"front.jpg","side-left.jpg","side-right.jpg","back.jpg"

Answer 1

select a.itemName, GROUP_CONCAT(b.itemImageName) 
from amga a 
left join amgb b 
on a.userId = b.userId 
where a.userId = 1
group by a.itemName

Use DISTINCT into GROUP_CONCAT if you dont want duplicates.

Answer 2

You need grouping with the GROUP_CONCAT function. Please try this query:

select a.itemName, group_concat(b.itemImageName) 
from amga a left join amgb b on a.userId = b.userId 
where a.userId = 1 
group by a.itemName;

Answer 3

The group_concat operator is what you're looking for:

SELECT    item_name, GROUP_CONCAT(item_image_name)
FROM      amga
LEFT JOIN amgb ON amga.userId = b.userId
WHERE     amge.userId = 1
GROUP BY  item_name